Field of the Invention
The present invention relates to an image forming apparatus.
Description of the Related Art
Many conventional image forming apparatuses such as copiers and printers use an electrostatic recording system, an electrophotographic system, or the like. Image forming apparatuses such as copiers and printers which are based on the electrophotographic system or the electrostatic recording system use a developing assembly using developer (hereinafter also referred to as toner). The developing assembly is provided with a developing chamber and a toner container in which toner is contained.
The developing chamber is provided with a developing roller (developer bearing member), and a toner feeding member that applies toner to a surface of the developing roller. The developing chamber is also provided with a toner regulating member that levels the toner coated by a toner feeding member on the surface of the developing roller into a more even thin layer. The thin layer of toner resulting from the leveling by the toner regulating member is conveyed out from the developing assembly in conjunction with rotation of the developing roller. The thin layer of toner attaches to an electrostatic latent image on a rotative photosensitive drum (image bearing member) disposed opposite an exposed portion of the developing roller, to visualize the electrostatic latent image. Thus, a toner image is formed on the photosensitive drum.
Before the developing assembly starts to be used, that is, when the developing assembly is new, the toner remains contained in the toner container. The toner is fed from the inside of the toner container into the developing chamber for the first time when the developing assembly starts to be used. Thus, before the developing assembly starts to be used, the developing roller is in direct contact with the toner regulating member and the toner feeding member with no toner present between the developing roller and the toner regulating member and toner feeding member. Consequently, torque may be increased in a driving system for the developing assembly.
Thus, in U.S. Pat. No. 3,397,510, the toner feeding member has a cell on the uppermost surface and has powder (toner or the like) with a particular charging capability at least on a front surface of the toner feeding member. This prevents the driving system for the developing assembly from being broken as a result of an increase in the driving torque on the developing assembly. Similarly, a technique is known in which a lubricant is coated on the developing roller to prevent the driving system for the developing assembly from being broken (U.S. Pat. No. 4,928,023).
In a new developing assembly, the toner in the toner container is provided with no charge. Thus, even when the toner is provided with charge at a contact region between the toner regulating member and the developing roller, the toner has difficulty immediately reaching an appropriate toner charge level. Consequently, sufficient developing performance may fail to be achieved, and density may be low or characters may be thin. Accordingly, in U.S. Pat. No. 4,261,941, the polarity of the lubricant coated on the developing roller is set opposite to the polarity of the toner to inhibit a decrease in density and in the thickness of characters at the stage where the developing assembly starts to be used.